The long-term objective of CCT is to develop and commercialize new transesophageal (TE) pacing systems. Available systems pace only the atria, but one, the other, or both heart chambers must be paced to satisfy temporary pacing needs in medical emergencies and Advanced Life Support protocols. This application describes clinical feasibility testing of prototype probes for TE atrial and/or ventricular pacing, including one for simultaneous pacing and electrocardiographic (ECG) monitoring. Available TE stimulators will be used for Phase I testing, and CCT's programmable TE stimulator developed and tested during Phase II. Because TE pacing is less costly and risky than epicardial or transvenous pacing, and more reliable and effective than transcutaneous pacing, it satisfies the need for a complete noninvasive pacing method. In anesthesiology, cardiology, critical care and emergency medicine, TE pacing can reduce drug use and replace other pacing methods for treatment of bradycardia or asystole. Further, TE-ECG with signal processing may be more sensitive and specific than other methods for detection of myocardial ischemia. It is believed that CCT's products can benefit 20 million surgical patients annually (U.S.), and several million more with life-threatening bradycardia due to cardiovascular disease or other causes. PROPOSED COMMERCIAL APPLICATION: Products for transesophageal (TE) pacing developed in this research will meet the urgent need for simpler, more reliable and effective, noninvasive temporary pacing devices for medical emergencies (advanced life support), both in and out of hospitals. Since TE pacing is simpler, more reliable and effective, or less costly than other pacing methods, it is expected to mostly replace current methods as the preferred initial pacing method. TE pacing has potential to be used by physicians, nurses or paramedics as treatment or prophylaxis for arrythmias in 25 million or more patients (U.S.).